Instruction/ maintenance manual of the product 7220 IBM
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Model 7220 DSP Lock-in Amplifier Instruction Manual 190171-A-MNL-C Copyright © 1996 EG&G INSTRUMENTS CORPORA TION.
FCC Notice This equipment generates, uses, and can radiate radio-frequency energy and, if not installed and used in accordance with this manual, may cause interference to radio communications.
T able of Contents i T able of Contents Chapter One, Introduction 1.1 How to Use This Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1 1.2 What is a Lock-in Amplifier? .
ii T ABLE OF CONTENTS 3.3.02 Relative Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-9 3.4 Full-Scale Sensitivity and AC Gain Control . . . . . . . . . . . . . . .
iii T ABLE OF CONTENTS 4.2.07 PREAMP POWER Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7 4.2.08 REF MON Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
iv T ABLE OF CONTENTS 6.3 RS232 and GPIB Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2 6.3.01 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
v T ABLE OF CONTENTS Appendix B, Pinouts B.1 RS232 Connector Pinout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1 B.2 Preamplifier Power Connector Pinout . . . . . . . . . .
vi T ABLE OF CONTENTS.
Introduction Chapter 1 1-1 1.1 How to Use This Manual This manual gives detailed instructions for setting up and operating the EG&G Instruments Model 7220 Digital Signal Processing (DSP) dual phase lock-in amplifier .
1-2 Chapter 1, INTRODUCTION Appendix D Shows the connection diagrams for suitable RS232 null-modem cables to couple the unit to an IBM-PC or 100 % compatible computer . Appendix E Gives an alphabetical listing of the computer commands for easy reference.
1-3 Chapter 1, INTRODUCTION 1.3 Key Specifications and Benefits The EG&G Instruments Model 7220 represents the latest in DSP Lock-in Amplifier technology at an af fordable price, and of fers:- n Fr equency range: 0.
1-4 Chapter 1, INTRODUCTION.
Installation & Initial Checks Chapter 2 2-1 2.1 Installation 2.1.01 Introduction Installation of the model 7220 in the laboratory or on the production line is very simple. Because of its low power consumption, the model 7220 does not incorporate forced-air ventilation.
2-2 Chapter 2, INST ALLA TION AND INITIAL CHECKS Instruments are normally shipped from the factory with the line voltage selector set to 1 10-130 V AC, unless they are destined for an area known to use a line voltage in the 220-260 V range, in which case, they are shipped configured for operation from the higher range.
2-3 Chapter 2, INST ALLA TION AND INITIAL CHECKS installed, close the plastic door firmly . The correct selected voltage setting should now be showing through the rectangular window . Ensure that only fuses with the required current rating and of the specified type are used for replacement.
2-4 Chapter 2, INST ALLA TION AND INITIAL CHECKS the CONTROL SETUP menu is displayed, which will look similar to the following:- Figure 2-3, Control Setup Menu 7) Press one of the keys on the right-hand side of the left-hand display once. This will set all the instrument’ s controls and displays to a known state.
T echnical Description Chapter 3 3-1 3.1 Introduction The model 7220 lock-in amplifier is capable of outstandingly good signal recovery performance, provided that it is operated correctly . This chapter describes the design of the instrument, enabling the best use to be made of its facilities.
3-2 Chapter 3, TECHNICAL DESCRIPTION 3.2.02 Signal-Channel Inputs The signal input amplifier may be configured for either single-ended or dif ferential voltage mode operation, or single-ended current mode operation. In voltage mode a choice of AC or DC coupling is available and the input may be switched between FET and bipolar devices.
3-3 Chapter 3, TECHNICAL DESCRIPTION The primary purpose of the DC coupling facility is to enable the use of the instrument at reference frequencies below 0.5 Hz. It may also be used to reduce the ef fect of phase and magnitude errors introduced by the AC coupling circuitry below a few hertz.
3-4 Chapter 3, TECHNICAL DESCRIPTION 3.2.04 AC Gain The signal channel contains a number of analog filters and amplifiers, the gain of which are defined by the “AC Gain” parameter , which is specified in terms of decibels (dB).
3-5 Chapter 3, TECHNICAL DESCRIPTION This alias signal is indistinguishable from the output generated when a genuine signal at frequency f alias is sampled.
3-6 Chapter 3, TECHNICAL DESCRIPTION There is one situation where this automatic correction might not be suf ficient to give good performance. Consider the case where the signal being measured is at 73 kHz, which is 10 kHz away from half the sampling frequency .
3-7 Chapter 3, TECHNICAL DESCRIPTION 3.2.08 Internal Oscillator The model 7220, in common with many other lock-in amplifiers, incorporates an internal oscillator which may be used to drive an experiment.
3-8 Chapter 3, TECHNICAL DESCRIPTION and Y channel output filters. The outputs of these in turn drive two 16-bit digital to analog converters (DACs) which generate the instrument’ s F AST X and F AST Y analog outputs.
3-9 Chapter 3, TECHNICAL DESCRIPTION 3.3.02 Relative Accuracy The majority of lock-in amplifier measurements are concerned with the variation of the input signal with time, temperature, etc.
3-10 Chapter 3, TECHNICAL DESCRIPTION reserve is often expressed in decibels, for which DR( in dB) = 20 log(DR( as a ratio)) Applying this formula to the model 7220 we may put in the maximum value of .
3-11 Chapter 3, TECHNICAL DESCRIPTION The circuits connected to the REF IN socket actually detect a positive-going crossing of the mean value of the applied reference voltage.
3-12 Chapter 3, TECHNICAL DESCRIPTION The 6 dB/octave filters are not satisfactory for most purposes because they do not give good rejection of periodic components in the demodulator output, including the inevitable component at double the reference frequency .
3-13 Chapter 3, TECHNICAL DESCRIPTION with respect to the reference input) and is computed by the output processor in the lock-in amplifier and made available as the “magnitude” output.
3-14 Chapter 3, TECHNICAL DESCRIPTION 3.10 Noise Measurements The noise measurement facility is available only in the baseband mode (i.e. at reference frequencies less than 60 kHz) and uses the output processor to perform a noise computation on the Y output where it is assumed that the waveform is Gaussian with zer o mean.
3-15 Chapter 3, TECHNICAL DESCRIPTION 3.12.02 Auto-Sensitivity This function only operates when the reference frequency is above 1 Hz. A single Auto-Sensitivity operation consists of increasing the fu.
3-16 Chapter 3, TECHNICAL DESCRIPTION 3.12.05 Auto-Measure This function only operates when the reference frequency is greater than 1 Hz. It performs the following operations: The line filter is disab.
Front and Rear Panels Chapter 4 4-1 4.1 Front Panel Figure 4-1, Model 7220 Front Panel Layout As shown in figure 4-1 there are four BNC connectors with associated LED indicators, two LCD display panels, an edge-indicating analog meter , eight double and three single keys mounted on the model 7220’ s front panel.
4-2 Chapter 4, FRONT AND REAR P ANELS 4.1.03 REF IN Connector This is the input connector for a general purpose external reference signal. When external reference mode is selected the LED adjacent to the connector will be lit (see figure 4-3). Under unlock conditions the LED will flash.
4-3 Chapter 4, FRONT AND REAR P ANELS precision. In these cases a significant number of keypresses are required to make adjustments. Adjustment of the latter type of control is made easier by the use of one or other of the two methods described below .
4-4 Chapter 4, FRONT AND REAR P ANELS Figure 4-6, Active Cursor Operation The double keypress action can also be performed with one finger by firmly pressing the center of the up and down ADJUST key rocker which will deform to press both keys. The active cursor can be used to set any particular digit.
4-5 Chapter 4, FRONT AND REAR P ANELS Figure 4-8, Setup Menu Mode - Left and Right-hand LCD Displays In the setup menu mode, the left-hand SELECT keys adjacent to the left-hand display cycle through a series of twelve setup menus.
4-6 Chapter 4, FRONT AND REAR P ANELS keypress” feature. T o perform such a switch, simply press both sides of the SELECT keys simultaneously . This feature avoids the need to cycle through a number of outputs, thereby reducing the number of keypresses needed.
4-7 Chapter 4, FRONT AND REAR P ANELS 4.2.03 RS232 Connector This 9-pin D type RS232 interface connector implements pins 1, 2, 3 and 7 (Earth Ground, T ransmit Data, Receive Data, Logic Ground) of a standard DTE interface.
4-8 Chapter 4, FRONT AND REAR P ANELS 4.2.1 1 CH1, CH2 Connectors The signal at these connectors is an analog voltage corresponding to a selected output, such as X, Y , R, θ , etc., as specified in the Output Setup menu. The minimum time constant that can be used is 5 ms.
Front Panel Operation Chapter 5 5-1 5.1 Introduction This chapter describes how to operate the model 7220 using the front panel controls, and describes its capabilities when used in this way . Chapter 6 provides similar information in the situation where the unit is operated remotely using one of the computer interfaces.
5-2 Chapter 5, FRONT P ANEL OPERA TION the right-hand display . The setup menu description is shown on the left-hand side of the left-hand display . Figure 5-1 makes this clear . One further press of the MENU key causes the instrument to leave the setup menu mode and return to the main display mode.
5-3 Chapter 5, FRONT P ANEL OPERA TION the front panel BNC connector marked “ B/I ”, and uses a low-noise (LN) current to voltage converter . Input This control has four settings:- Flt/DC The shells of the “ A ” and “ B/I ” connectors are connected to chassis ground via a 1 k Ω resistor and the signal channel input is DC coupled.
5-4 Chapter 5, FRONT P ANEL OPERA TION 5.2.02 Reference Setup Menu Figure 5-3, Reference Setup Menu In this menu, shown in figure 5-3, there are three controls af fecting the reference channel of the instrument.
5-5 Chapter 5, FRONT P ANEL OPERA TION ON When the Demodulator Monitor is switched ON and the instrument is operating in External Reference mode, the signal at the OSC OUT connector changes from that of the internal oscillator to an analog representation of the drive from the reference channel to the X output demodulator .
5-6 Chapter 5, FRONT P ANEL OPERA TION OFF Output expansion is turned off. X ONLY A ×10 output expansion is applied to the X output only . Y ONLY A ×10 output expansion is applied to the Y output only . X & Y A ×10 output expansion is applied to both the X and Y outputs.
5-7 Chapter 5, FRONT P ANEL OPERA TION MAG %fs CH1/2 V oltage +120 12.0 V +100 10.0 V 0 0.0 V -100 -10.0 V -120 -12.0 V PHASE1 When set to PHASE1 the corresponding rear panel CH1/CH2 connector will output a voltage related to the PHA deg front panel display as follows:- PHA deg CH1/2 V oltage +180 9.
5-8 Chapter 5, FRONT P ANEL OPERA TION 5.2.04 Control Options Menu Figure 5-5, Control Options Setup Menu This menu, shown in figure 5-5, has three controls af fecting the line frequency rejection fil.
5-9 Chapter 5, FRONT P ANEL OPERA TION MANUAL In this setting the AC Gain may be manually adjusted from the main display . AUTOMATIC In this setting the AC Gain value is automatically selected by the instrument, depending on the full-scale sensitivity .
5-10 Chapter 5, FRONT P ANEL OPERA TION 5.2.05 Miscellaneous Options Menu Figure 5-6, Miscellaneous Options Setup Menu This menu, shown in figure 5-6, has three controls af fecting the auxiliary ADC t.
5-11 Chapter 5, FRONT P ANEL OPERA TION 5.2.06 RS232 Setup 1 Menu Figure 5-7, RS232 Setup 1 Menu This menu, shown in figure 5-7, has three controls affecting the RS232 computer interface, as follows:- BaudRate Thirteen values of Baud Rate are available in the range 75 to 19200 bits per second.
5-12 Chapter 5, FRONT P ANEL OPERA TION 5.2.07 RS232 Setup 2 Menu Figure 5-8, RS232 Setup 2 Menu This menu, shown in figure 5-8, has three controls af fecting the RS232 computer interface, as follows:.
5-13 Chapter 5, FRONT P ANEL OPERA TION MP command (report Magnitude and Phase). Hence it is necessary for the controlling program to be able to determine when all of the first value has been sent. The delimiter is a separator character sent between each response which may be used for this purpose.
5-14 Chapter 5, FRONT P ANEL OPERA TION 5.2.09 GPIB Setup 1 Menu Figure 5-10, GPIB Setup 1 Menu This menu, shown in figure 5-10, has two controls af fecting the GPIB computer interface, as follows:- Address Each instrument used on the GPIB interface must have a unique address, in the range 0 to 31, and this control is used to set this address.
5-15 Chapter 5, FRONT P ANEL OPERA TION 5.2.10 GPIB Setup 2 Menu Figure 5-1 1, GPIB Setup 2 Menu This menu, shown in figure 5-1 1, has two controls affecting the GPIB computer interface, as follows:- .
5-16 Chapter 5, FRONT P ANEL OPERA TION 5.2.1 1 Digital Outputs Setup Menu Figure 5-12, Digital Outputs Setup Menu This menu, shown in figure 5-12, is used to control the 8 TTL lines of the rear panel digital output port, used for controlling external equipment.
5-17 Chapter 5, FRONT P ANEL OPERA TION 5.2.12 Control Setup Menu Figure 5-13, Control Setup Menu The final setup menu, shown in figure 5-13, is used to set the instrument to a known state and to adjust the sampling rate of the main analog to digital converter .
5-18 Chapter 5, FRONT P ANEL OPERA TION 5.3 Auto Functions Menu When in the Main Display mode, one press of the MENU key accesses the AUT O MENU showing four auto functions that are built into the instrument. The left-hand LCD changes to that shown in figure 5-14.
5-19 Chapter 5, FRONT P ANEL OPERA TION are steady , implying the signal phase is stable, when the procedure is called. If a zero error is present on the outputs, such as may be caused by unwanted cou.
5-20 Chapter 5, FRONT P ANEL OPERA TION The line filter is disabled; AC coupling is established; the voltage measurement mode is entered, using the single-ended, A, input; the FET input devices are enabled; the FLOA T mode is set.
5-21 Chapter 5, FRONT P ANEL OPERA TION Figure 5-15, Sensitivity Control - V oltage Input Mode When set to current input mode, the instrument’ s full-scale current sensitivity may be set to any value between 20 fA and 1 µA (wide bandwidth mode) or 20 fA and 10 nA (low-noise mode), in a 1-2-5 sequence.
5-22 Chapter 5, FRONT P ANEL OPERA TION AC Gain If the AC Gain control is set to Manual (using the Input Setup menu), then this control allows it to be adjusted from 0 dB to 90 dB in 10 dB steps, although not all settings are available at all full-scale sensitivity settings.
5-23 Chapter 5, FRONT P ANEL OPERA TION Slope The roll-off of the output filters is set, using this control, to any value from 6 dB to 24 dB/octave, in 6 dB steps. Note this control does not af fect the roll-off of outputs at the F AST X and F AST Y connectors which are fixed at 6 dB/octave.
5-24 Chapter 5, FRONT P ANEL OPERA TION Oscillator Amplitude The amplitude of the instrument’ s internal oscillator may be set, using this control, to any value between 1 mV and 5 V rms with a 1 mV resolution. Adjustment is faster if use is made of the Active Cursor control - see section 4.
5-25 Chapter 5, FRONT P ANEL OPERA TION DAC 2 This control sets the voltage appearing at the rear panel DAC2 output connector to any value between +10 V and -10 V with a resolution of 1 mV . Adjustment is faster if use is made of the Active Cursor control - see section 4.
5-26 Chapter 5, FRONT P ANEL OPERA TION Refer ence Phase This control allows the reference phase to be adjusted over the range -360° to + 360° in 10m° steps, although readers will appreciate that a setting of -180° is equivalent to +180°, and that ±360° is equivalent to 0°.
5-27 Chapter 5, FRONT P ANEL OPERA TION X %fs Figure 5-27, X Output as % Full-Scale Shows the X output as a percentage of the selected full-scale sensitivity setting. Hence if the sensitivity setting were 100 mV and a 50 mV signal were applied, with the instrument’ s reference phase adjusted for maximum X output, the display would read 50.
5-28 Chapter 5, FRONT P ANEL OPERA TION MAG %fs Figure 5-29, Magnitude Output as % Full-Scale Shows the signal magnitude, where magnitude = √ ((X output) 2 + Y output) 2 ), as a percentage of the selected full-scale sensitivity setting.
5-29 Chapter 5, FRONT P ANEL OPERA TION Phase in Degr ees Figure 5-31, Phase Output in Degrees Shows the relative phase, where phase = tan -1 (Y output/X output), in degrees. Refer ence Fr equency Figure 5-32, Reference Frequency Display Shows the reference frequency at which the lock-in amplifier is operating.
5-30 Chapter 5, FRONT P ANEL OPERA TION X V olts (or Amps) Figure 5-33, X Output in V olts or Amps Shows the X output directly in terms of volts or amps (depending on whether voltage or current input mode is selected).
5-31 Chapter 5, FRONT P ANEL OPERA TION MAG V olts (or Amps) Figure 5-35, Magnitude Output in V olts or Amps Shows the signal magnitude, where magnitude = √ ((X output) 2 + (Y output) 2 ), directly in terms of volts or amps (depending on whether voltage or current input mode is selected).
5-32 Chapter 5, FRONT P ANEL OPERA TION Ratio Figure 5-37, Ratio Output Shows the ratio, where ratio = (X output / ADC1 Input), usually used to compensate for source intensity fluctuations in optical experiments.
5-33 Chapter 5, FRONT P ANEL OPERA TION ADC1 V olts Figure 5-39, ADC 1 Input Shows the voltage applied to the rear panel ADC1 auxiliary input. ADC2 V olts Figure 5-40, ADC 2 Input Shows the voltage applied to the rear panel ADC2 auxiliary input.
5-34 Chapter 5, FRONT P ANEL OPERA TION X Offset Figure 5-41, X Output Offset Control This control allows the X output of fset to be adjusted, using the lower ADJUST keys adjacent to the displayed value.
5-35 Chapter 5, FRONT P ANEL OPERA TION warning message OFFSET! The instrument provides a quick way to switch between the following pairs of outputs, by simply pressing simultaneously both ends of the.
5-36 Chapter 5, FRONT P ANEL OPERA TION.
Computer Operation Chapter 6 6-1 6.1 Introduction The model 7220 includes both RS232 and IEEE-488 (also known as GPIB for General Purpose Interface Bus) interface ports, designed to allow the lock-in amplifier to be completely controlled from a remote computer .
6-2 Chapter 6, COMPUTER OPERA TION 6.2.04 Internal Oscillator Frequency Sweep Generator The instrument’ s internal oscillator may be swept in frequency both linearly and logarithmically over a specified range.
6-3 Chapter 6, COMPUTER OPERA TION The main advantages of the RS232 interface are: 1 . It communicates via a serial port which is present as standard equipment on nearly all computers, using leads and connectors which are available from suppliers of computer accessories or can be constructed at minimal cost in the user’ s workshop.
6-4 Chapter 6, COMPUTER OPERA TION Where the RS232 parameters of the terminal or computer are capable of being set to any desired value, an arbitrary choice must be made. In the model 7220 the combination set at the factory is even parity check, 7 data bits, and one stop bit (fixed) because these are the MS-DOS default.
6-5 Chapter 6, COMPUTER OPERA TION Because of the parallel nature of the GPIB and its very effective use of the control lines including the implementation of a three-wire handshake (see below), comparatively high data rates are possible, up to a few hundred thousand bytes per second.
6-6 Chapter 6, COMPUTER OPERA TION parameter byte. The default (power-up) state of this bit is for it to be asserted. The program RSCOM2.BAS in section C.
6-7 Chapter 6, COMPUTER OPERA TION sent without the optional parameters, the response consists of a transmission of the present values of the parameter(s).
6-8 Chapter 6, COMPUTER OPERA TION respectively . In GPIB communications, the use of these bits can lead to a useful simplification of the control program by providing a response subroutine which is the same for all commands, whether or not they send a response over the bus.
6-9 Chapter 6, COMPUTER OPERA TION 6.3.14 Service Requests The interface defined by the IEEE-488 standard includes a line (pin 10 on the connector) called the SRQ (service request) line which is used by the instrument to signal to the controller that ur gent attention is required.
6-10 Chapter 6, COMPUTER OPERA TION 6.4 Command Descriptions This section lists the commands in logical groups, so that, for example, all commands associated with setting controls af fecting the signal channel are shown together . Appendix E gives the same list of commands but in alphabetical order .
6-11 Chapter 6, COMPUTER OPERA TION CP [n] Input coupling control The value of n sets the input coupling mode according to the following table: n Coupling mode 0A C 1D C SEN[.
6-12 Chapter 6, COMPUTER OPERA TION ASM Perform an Auto-Measure operation The instrument adjusts its full-scale sensitivity so that the magnitude output lies between 30 % and 90 % of full-scale, and then performs an auto-phase operation to maximize the X output and minimize the Y output.
6-13 Chapter 6, COMPUTER OPERA TION n Notch filter mode 0 60 Hz (and/or 120 Hz) 1 50 Hz (and/or 100 Hz) Units made prior to June 1996 generate an Invalid Command (bit 1 of the serial poll status byte is asserted) to the LINE50 command.
6-14 Chapter 6, COMPUTER OPERA TION FRQ[.] Reference frequency meter If the lock-in amplifier is in the EXT or EXT LOGIC reference source modes, the FRQ command causes the lock-in amplifier to respond with 0 if the reference channel is unlocked, or with the reference input frequency if it is locked.
6-15 Chapter 6, COMPUTER OPERA TION 17 10 s 18 20 s 19 50 s 20 100 s 21 200 s 22 500 s 23 1 ks 24 2 ks 25 5 ks The TC. command is only used for reading the time constant, and reports the current setting in seconds. Hence if a TC 1 1 command were sent, TC would report 1 1 and TC.
6-16 Chapter 6, COMPUTER OPERA TION AXO Auto-Offset The X and Y output of fsets are turned on and set to levels giving zero X and Y outputs. Any changes in the input signal then appear as changes about zero in the outputs. EX [n] Output expansion control Expands X and/or Y outputs by a factor of 10.
6-17 Chapter 6, COMPUTER OPERA TION XY[.] X, Y outputs Equivalent to the compound command X[.];Y[.] MAG[.] Magnitude In fixed point mode causes the lock-in amplifier to respond with the magnitude value in the range 0 to 30000, full-scale being 10000.
6-18 Chapter 6, COMPUTER OPERA TION ENBW[.] Equivalent noise bandwidth In fixed point mode, reports the equivalent noise bandwidth of the output low-pass filters at the current time constant setting in microhertz.
6-19 Chapter 6, COMPUTER OPERA TION Caution: Check that the computer program does not automatically add a carriage return or carriage return-line feed terminator to the * command, since these characters will slow down communications. 6.4.06 Internal Oscillator OA[.
6-20 Chapter 6, COMPUTER OPERA TION FSTEP[.] [n 1 n 2 ] Oscillator frequency sweep step size and type The frequency may be swept either linearly or logarithmically , as specified by parameter n 2 . The step size is specified by parameter n 1 . Log sweep n 2 = 0 In fixed point mode, n 1 is the step size in thousandths of a percent.
6-21 Chapter 6, COMPUTER OPERA TION BYTE [n] Digital output port control The value of n, in the range 0 to 255, determines the bits to be output on the rear panel digital output port. When n = 0, all outputs are low , and when n = 255, all are high. 6.
6-22 Chapter 6, COMPUTER OPERA TION T ADC parameter Ef fect on CBD parameter 0 none 1 none 2 automatically set to 32 3 automatically set to 96 4 automatically set to 32 5 automatically set to 96 6 aut.
6-23 Chapter 6, COMPUTER OPERA TION 6.4.09 Output Data Curve Buffer CBD [n] Curve buffer define Defines which data outputs are stored in the curve buf fer when subsequent TD (take data) or TDC (take data continuously) commands are issued. Up to 16 curves, or outputs, may be acquired, as specified by the CBD parameter .
6-24 Chapter 6, COMPUTER OPERA TION and HC commands. It also interacts with the LEN command and af fects the values reported by the M command. LEN [n] Curve length control The value of n sets the curve buf fer length in ef fect for data acquisition.
6-25 Chapter 6, COMPUTER OPERA TION HC Halt curve acquisition Halts curve acquisition in progress. It is ef fective during both single (data acquisition initiated by TD command) and continuous (data acquisition initiated by TDC command) curve acquisitions.
6-26 Chapter 6, COMPUTER OPERA TION The computer program’ s subroutine which reads the responses to the DC command needs to run a FOR...NEXT loop of length equal to the value set by the LEN (curve length) command. Note that when using this command with the GPIB interface the serial poll must be used.
6-27 Chapter 6, COMPUTER OPERA TION <X output value 1 ><delim><Magnitude value 1 ><term> <X output value 2 ><delim><Magnitude value 2 ><term> <X outp.
6-28 Chapter 6, COMPUTER OPERA TION bit number bit negated bit asserted 0 data + parity = 8 bits data + parity = 9 bits 1 no parity bit 1 parity bit 2 even parity odd parity 3 echo disabled echo enabl.
6-29 Chapter 6, COMPUTER OPERA TION byte is accessed by performing a serial poll. Bit 0 Command complete Bit 1 Invalid command Bit 2 Command parameter error Bit 3 Reference unlock Bit 4 Overload Bit 5.
6-30 Chapter 6, COMPUTER OPERA TION 6.4.12 Front Panel L T S [n] Lights on/of f control The value of n controls the front panel LEDs and LCD backlights according to the following table: n Selection 0 All lights off 1 Normal operation 6.
6-31 Chapter 6, COMPUTER OPERA TION The controlling program would send a new output command each time a new reading were required. Note that a good “rule of thumb” is to wait for a period of five time- constants after the input signal has changed before recording a new value.
6-32 Chapter 6, COMPUTER OPERA TION 6.5.04 X and Y Output Curve Storage Measurement In this example, the lock-in amplifier is measuring a current input signal applied to the B input connector and the measured X output and Y output are recorded for 10 seconds at a 100 Hz sampling rate.
6-33 Chapter 6, COMPUTER OPERA TION NC Clear and reset curve buf fer LEN 20000 500 ms recording time at 40 kHz = 20,000 points T ADC 6 Set ADC1 sampling to burst mode, fixed rate ( ≈ 40 kHz), external trigger, and arm trigger As soon as a trigger occurs, the acquisition starts.
6-34 Chapter 6, COMPUTER OPERA TION NC Clear and reset curve buf fer CBD 49180 Stores Magnitude, Phase, Sensitivity and Frequency (i.e. bits 2, 3, 4, 14 and 15) LEN 100 Number of points = 100 STR 100 .
Specifications Appendix A A-1 Measurement Modes X In-phase Y Quadrature The unit can simultaneously present any R Magnitude two of these as outputs θ Phase Angle Noise Harmonic 2F.
A-2 Appendix A, SPECIFICA TIONS Current Input Mode Low Noise or W ide Bandwidth Full-scale Sensitivity Low Noise 20 fA to 10 nA in a 1-2-5 sequence W ide Bandwidth 20 fA to 1 µA in a 1-2-5 sequence D.
A-3 Appendix A, SPECIFICA TIONS Orthogonality 90º ±0.0001º Drift < 0.01º/ºC below 10 kHz < 0.1º/ºC above 10 kHz Acquisition T im e Internal Reference instantaneous acquisition External Reference 2 cycles + 50 ms Reference Frequency Meter Accuracy 120 kHz > F > 40 kHz ±4 Hz 40 kHz > F > 400 Hz ±0.
A-4 Appendix A, SPECIFICA TIONS Amplitude Range 1 m V t o 5 V Setting Resolution 1 mV to 500 mV 1 mV 501 mV to 2 V 4 mV 2.001 V to 5 V 10 mV Accuracy 0.001 Hz to 60 kHz ±0.3 % 60 kHz to 120 kHz ±0.5 % Stability 50 ppm/ºC Output Impedance 50 Ω Auxiliary Inputs ADC 1 and 2 Maximum Input ±10 V Resolution 1 mV Accuracy ±0.
A-5 Appendix A, SPECIFICA TIONS Signal Monitor Amplitude ±10 V FS Impedance 1 k Ω Aux D/A Output 1, 2 Maximum Output ±10 V Resolution 1 mV Accuracy ±0.
A-6 Appendix A, SPECIFICA TIONS General Dimensions W idth 432 mm (17 ") Depth 415 mm (16.4 ") Height W ith feet 74 mm (2.9 ") W ithout feet 60 mm (2.
Pinouts Appendix B B-1 B.1 RS232 Connector Pinout 1 2 3 4 6 7 8 5 9 Figure B-1, RS232 and AUX RS232 Connector (Female) PI N FUNCTION COMMENT 2 RXD Data In 3 TX D Data Out 5 GN D Signal Ground 7 R T S (Always at +12 V) All other pins are not connected.
B-2 Appendix B, PINOUTS B.3 Digital Output Port Connector Figure B-3, Digital Output Port Connector 8-bit TTL-compatible output set from the front panel or via the computer interfaces; each line can drive 3 LSTTL loads. This connector mates with a 20-pin IDC Header Plug.
Demonstration Programs Appendix C C-1 C.1 Simple T erminal Emulator This is a short terminal emulator with minimal facilities, which will run on a PC-compatible computer in a Microsoft GW-BASIC or QuickBASIC environment, or can be compiled with a suitable compiler .
C-2 Appendix C, DEMONSTRA TION PROGRAMS 1 00 B$=B$+CR$ ' append a carriage return 1 10 GOSUB 180 ' output the command B$ 1 20 GOSUB 310: PRINT Z$; ' read and display response 1 30 IF A$.
C-3 Appendix C, DEMONSTRA TION PROGRAMS C.3 GPIB User Interface Program GPCOM.BAS is a user interface program which illustrates the principles of the use of the serial poll status byte to coordinate the command and data transfer .
C-4 Appendix C, DEMONSTRA TION PROGRAMS 290 V%=1 1: CALL IBTMO(DEV%,V%) 300 '....set status print flag........................ 310 INPUT "Display status byte y/n "; R$ 320 IF R$="Y" OR R$="y" THEN DS% = 1 ELSE DS% = 0 330 '.
Cable Diagrams Appendix D D-1 D.1 RS232 Cable Diagrams Users who choose to use the RS232 interface to connect the model 7220 lock-in amplifier to a standard serial port on a computer , will need to use one of two types of cable. The only dif ference between them is the number of pins used on the connector which goes to the computer .
D-2 Appendix D, CABLE DIAGRAMS Figure D-2, Interconnecting RS232 Cable Wiring Diagram.
Alphabetical Listing of Commands Appendix E E-1 ACGAIN [n] AC Gain control Sets the gain of the signal channel amplifier . V alues of n from 0 to 9 can be entered corresponding to the range 0 dB to 90 dB in 10 dB steps.
E-2 Appendix E, ALPHABETICAL LISTING OF COMMANDS AXO Auto-Offset The X and Y output of fsets are turned on and set to levels giving zero X and Y outputs.
E-3 Appendix E, ALPHABETICAL LISTING OF COMMANDS Bi t Decimal value Output and range 0 1 X Output (±10000 FS) 1 2 Y Output (±10000 FS) 2 4 Magnitude Output (±10000 FS) 3 8 Phase (±18000 = ±180°) 4 16 Sensitivity setting (4 to 27) + IMODE (0, 1, 2 = 0, 32, 64) 5 32 ADC1 (±10000 = ±10.
E-4 Appendix E, ALPHABETICAL LISTING OF COMMANDS CH n 1 [n 2 ] Analog output control Defines what outputs appear on the rear panel CH1 and CH2 connectors according to the following table: n 2 Signal 0.
E-5 Appendix E, ALPHABETICAL LISTING OF COMMANDS The computer program’ s subroutine which reads the responses to the DC command needs to run a FOR...NEXT loop of length equal to the value set by the LEN (curve length) command. Note that when using this command with the GPIB interface the serial poll must be used.
E-6 Appendix E, ALPHABETICAL LISTING OF COMMANDS <X output value 1 ><delim><Magnitude value 1 ><term> <X output value 2 ><delim><Magnitude value 2 ><term&g.
E-7 Appendix E, ALPHABETICAL LISTING OF COMMANDS EX [n] Output expansion control Expands X and/or Y outputs by a factor of 10. Changes meter , CH1 and CH2 outputs full-scale to ±10 % if X or Y selected.
E-8 Appendix E, ALPHABETICAL LISTING OF COMMANDS FST AR T[.] [n] Oscillator frequency sweep start frequency Sets the start frequency for a subsequent sweep of the internal oscillator frequency . In fixed point mode, n is in millihertz. In floating point mode n is in hertz.
E-9 Appendix E, ALPHABETICAL LISTING OF COMMANDS HC Halt curve acquisition Halts curve acquisition in progress. It is ef fective during both single (data acquisition initiated by TD command) and continuous (data acquisition initiated by TDC command) curve acquisitions.
E-10 Appendix E, ALPHABETICAL LISTING OF COMMANDS LF [n] Signal channel line frequency rejection filter control In instruments manufactured prior to June 1996, the value of n sets the mode of the line frequency notch filter according to the following table: n Selection 0O f f 1 On (i.
E-11 Appendix E, ALPHABETICAL LISTING OF COMMANDS L T S [n] Lights on/of f control The value of n controls the front panel LEDs and LCD backlights according to the following table: n Selection 0 All l.
E-12 Appendix E, ALPHABETICAL LISTING OF COMMANDS N n Address command When the 7220 is daisy-chained with other compatible instruments this command will change which instrument is addressed. All daisy-chained instruments receive commands but only the currently addressed instrument will implement or respond to the commands.
E-13 Appendix E, ALPHABETICAL LISTING OF COMMANDS OA[.] [n] Oscillator amplitude control In fixed point mode n sets the oscillator amplitude in mV . The range of n is 0 to 5000 representing 0 to 5 V rms. In floating point mode n sets the amplitude in volts.
E-14 Appendix E, ALPHABETICAL LISTING OF COMMANDS RS [n 1 [n 2 ] ] Set/read RS232 interface parameters The values of n 1 set the baud rate of the RS232 interface according to the following table: n 1 Baud rate (bits per second) 07 5 1 110 2 134.
E-15 Appendix E, ALPHABETICAL LISTING OF COMMANDS SEN[.] [n] Full-scale sensitivity control The value of n sets the full-scale sensitivity according to the following table, depending on the setting of.
E-16 Appendix E, ALPHABETICAL LISTING OF COMMANDS ST Report status byte Causes the lock-in amplifier to respond with the status byte. Note: this command is not normally used in GPIB communications, where the status byte is accessed by performing a serial poll.
E-17 Appendix E, ALPHABETICAL LISTING OF COMMANDS return or carriage return-line feed terminator to the * command, since these characters will slow down communications. STR [n] Storage interval control Sets the time interval between successive points being acquired under the TD or TDC commands.
E-18 Appendix E, ALPHABETICAL LISTING OF COMMANDS SYNCOSC [n] Synchronous oscillator (demodulator monitor) control This control operates only in external reference mode.
E-19 Appendix E, ALPHABETICAL LISTING OF COMMANDS The maximum sampling rate depends on the number of ADC inputs used and whether the sampling is timed or simply runs as fast as possible.
E-20 Appendix E, ALPHABETICAL LISTING OF COMMANDS TD C T ake data continuously Initiates data acquisition. Acquisition starts at the current position in the curve buf f er and continues at the rate set by the STR command until halted by an HC command.
E-21 Appendix E, ALPHABETICAL LISTING OF COMMANDS YOF [n 1 [n 2 ] ] Y output of fset control The value of n 1 sets the status of the Y of fset facility according to the following table: n 1 Selection 0 Disables offset facility 1 Enables of fset facility The range of n 2 is ±30000 corresponding to ±300 % full-scale.
E-22 Appendix E, ALPHABETICAL LISTING OF COMMANDS.
Default Settings Appendix F F-1 Default Setting Function The default setting function sets the model 7220’ s controls and output displays as follows:- Left-hand LCD Displays the AC Gain control on the upper line and the full-scale sensitivity control on the lower line.
F-2 Appendix F , DEF AUL T SETTINGS Line frequency rejection filter Off AC Gain control Manual T ime constant mode Sync ADC trigger rate 200 Hz Front panel lights O n Display contrast 0 RS232 interfac.
Index Index Index-1 * command 6-18, E-16 N n command 6-28, E-12 2F reference mode 3-7, 5-4 8-bit programmable output port 3-8 90° Key 4-5 Absolute accuracy 3-8 AC Gain and full-scale sensitivity 3-9 .
Index-2 INDEX Computer control, sample programs 6-30 Contrast control 5-10 Control options menu 5-8 Control setup menu 5-17 CP [n] command 6-1 1, E-4 Current input mode 3-2, 5-2 Current to voltage converter 5-2 Current/voltage input mode selection 3-3 Curve storage 6-1 DAC[.
Index-3 INDEX Input connector ground/float 5-3 connector selection 5-2 connector shell ground/float 3-2 coupling 3-2, 5-3 device selection 3-2, 5-3 float/ground control 3-2 impedance 3-2, 5-3 mode 5-2.
Index-4 INDEX Ratio display 5-32 RA TIO output 5-7 Rear panel layout 4-6 REF IN connector 3-10, 4-2, 5-4 REF MON connector 4-7 REF TTL connector 4-7, 5-4 Reference channel DSP 3-6 Reference frequency .
Index-5 INDEX Update program 3-8 V ector magnitude 3-8 V entilation 2-1 VER command 6-29, E-20 VMODE [n] command 6-10, E-20 V oltage input mode 3-2 What is a lock-in amplifier? 1-2 X % output 5-6 X %fs display 5-27 X & Y demodulation functions 3-7 X in volts/amps display 5-30 X output of fset level control 5-34 X[.
Index-6 INDEX.
W ARRANTY EG&G Instruments Corporation warrants each instrument of its own manufacture to be free of defects in material and workmanship for a period of ONE year from the date of delivery to the original purchaser .
An important point after buying a device IBM 7220 (or even before the purchase) is to read its user manual. We should do this for several simple reasons:
If you have not bought IBM 7220 yet, this is a good time to familiarize yourself with the basic data on the product. First of all view first pages of the manual, you can find above. You should find there the most important technical data IBM 7220 - thus you can check whether the hardware meets your expectations. When delving into next pages of the user manual, IBM 7220 you will learn all the available features of the product, as well as information on its operation. The information that you get IBM 7220 will certainly help you make a decision on the purchase.
If you already are a holder of IBM 7220, but have not read the manual yet, you should do it for the reasons described above. You will learn then if you properly used the available features, and whether you have not made any mistakes, which can shorten the lifetime IBM 7220.
However, one of the most important roles played by the user manual is to help in solving problems with IBM 7220. Almost always you will find there Troubleshooting, which are the most frequently occurring failures and malfunctions of the device IBM 7220 along with tips on how to solve them. Even if you fail to solve the problem, the manual will show you a further procedure – contact to the customer service center or the nearest service center
